I've successfully created three-way bookshelf speakers containing a 10" woofer, a 2" dome midrange, and a 1" tweeter per closed enclosure for years. The crossovers are tuned to have output response (nearly) summing flat as shown in this picture.
However, I've been using them with an active subwoofer. Now I plan to stop using subwoofer and would like to listen to low-frequency from the main speakers. I removed subwoofer and found the bass wasn't enough, though I reckon these speakers sound flat.
I still have a pair of the woofers unused so I thought to add them to the system. In other words, the bookshelf speakers will be converted to floor-standing from now on.
The problem is I cannot easily add them without mod the crossovers. And I want to increase only low-frequency region. I finally need to convert them to 3.5-way system. In fact, I tried building them 3-way by typical way of adding the second woofer and redo the whole crossovers and found the unsatisfied result when there's no upgrading in bass SPL increasing anymore. Thus, I realized the 3.5-way system may correctly fix the problem.
Here is the simulation of the 3.5-way system that I randomly generated in simulation software.
I confess I don't have knowledge about the procedure or theory for building 3.5-way system. I simply add a second woofer with twice larger inductor on it, the 14mH coil.
And this is the comparison between 3-way and 3.5-way systems.
I would like to ask whether I did it correctly? And is the result (simulation graph) acceptable? I know the more accurate version should be from real measurement not simulation result, but this is the first step of learning. So, please try to understand.
However, I've been using them with an active subwoofer. Now I plan to stop using subwoofer and would like to listen to low-frequency from the main speakers. I removed subwoofer and found the bass wasn't enough, though I reckon these speakers sound flat.
I still have a pair of the woofers unused so I thought to add them to the system. In other words, the bookshelf speakers will be converted to floor-standing from now on.
The problem is I cannot easily add them without mod the crossovers. And I want to increase only low-frequency region. I finally need to convert them to 3.5-way system. In fact, I tried building them 3-way by typical way of adding the second woofer and redo the whole crossovers and found the unsatisfied result when there's no upgrading in bass SPL increasing anymore. Thus, I realized the 3.5-way system may correctly fix the problem.
Here is the simulation of the 3.5-way system that I randomly generated in simulation software.
I confess I don't have knowledge about the procedure or theory for building 3.5-way system. I simply add a second woofer with twice larger inductor on it, the 14mH coil.
And this is the comparison between 3-way and 3.5-way systems.
I would like to ask whether I did it correctly? And is the result (simulation graph) acceptable? I know the more accurate version should be from real measurement not simulation result, but this is the first step of learning. So, please try to understand.
Let me explain further about the reason for going from 3 to 3.5-way.
When adding a second woofer the woofers section’s SPL will be louder than mid & high about 6dB. And the woofers are crossed at 350Hz. This means from zero up to 350Hz range will be lifted. Although bass was boosted to satisfactory, mid-bass would also be boosted causing too rich male voice, “Ummm” sound, or called mid-bass boom. To fix this, I tried lowering x-over point of the woofers, but that would introduce a gap between woofer and midrange resulting in too thin voice instead while the mid-bass boom still existed. That’s awful situation literally. And lowering the x-over of the midrange isn’t possible because it’s limited by physical of the 2” dome midranges, they can’t play any lower frequency plotted on graph. Adding a mid-bass driver and go for 4-way isn’t worthwhile because I still have a pair of the same woofers. Therefore, the only thing I could think of is to go 3.5-way.
When adding a second woofer the woofers section’s SPL will be louder than mid & high about 6dB. And the woofers are crossed at 350Hz. This means from zero up to 350Hz range will be lifted. Although bass was boosted to satisfactory, mid-bass would also be boosted causing too rich male voice, “Ummm” sound, or called mid-bass boom. To fix this, I tried lowering x-over point of the woofers, but that would introduce a gap between woofer and midrange resulting in too thin voice instead while the mid-bass boom still existed. That’s awful situation literally. And lowering the x-over of the midrange isn’t possible because it’s limited by physical of the 2” dome midranges, they can’t play any lower frequency plotted on graph. Adding a mid-bass driver and go for 4-way isn’t worthwhile because I still have a pair of the same woofers. Therefore, the only thing I could think of is to go 3.5-way.
is the second bass the same as the first one?
if yes put them in series the efficiency won't rise then. Adjust the crossover of the bass to the new impedance.
If its another bass I won't add it to the system but try to convert the closed box to a bass reflex design.
The box will be bigger. The qts should not get too high, check the parameters for this.
if yes put them in series the efficiency won't rise then. Adjust the crossover of the bass to the new impedance.
If its another bass I won't add it to the system but try to convert the closed box to a bass reflex design.
The box will be bigger. The qts should not get too high, check the parameters for this.
If you actually 'have your hands on' a pair of 14mH inductors as indicated in the circuit diagram above >
I have a very adventurous project for you to try >
1. You separate the "Lower (sub) Woofer" and its 14mH inductor from all other crossover components. This means the 'sub' will be its own independent
circuit connected to the amplifier. [ with the possibility of a series resistor needed ]
2. You mount the 'sub' Face to the rear of the speaker box. In this way, you slightly add some volume to the enclosure, rather than subtracting.
3. You add a 'blanket of 1cm felt' > glued to the interior of the wood cut-out > this makes the 'sub' think it is seeing a larger box.
This scenario could be called "an actively assisted rear port" OR "an actively assisted rear passive radiator" but with far more output >
Giving you SUB output 🙂
When such a design is located in the region of a room corner, a horn-loading effect can come into play greatly increasing Low Bass output.
[ a resistor or EQ may be required to customize/tame things ]
The Phase orientation/wiring of the rear driver WILL be immediately obvious when you get it right.
PS.
I have used this design, and it is quite amazing. [ driver & enclosure obviously dependent ]
I have a very adventurous project for you to try >
1. You separate the "Lower (sub) Woofer" and its 14mH inductor from all other crossover components. This means the 'sub' will be its own independent
circuit connected to the amplifier. [ with the possibility of a series resistor needed ]
2. You mount the 'sub' Face to the rear of the speaker box. In this way, you slightly add some volume to the enclosure, rather than subtracting.
3. You add a 'blanket of 1cm felt' > glued to the interior of the wood cut-out > this makes the 'sub' think it is seeing a larger box.
This scenario could be called "an actively assisted rear port" OR "an actively assisted rear passive radiator" but with far more output >
Giving you SUB output 🙂
When such a design is located in the region of a room corner, a horn-loading effect can come into play greatly increasing Low Bass output.
[ a resistor or EQ may be required to customize/tame things ]
The Phase orientation/wiring of the rear driver WILL be immediately obvious when you get it right.
PS.
I have used this design, and it is quite amazing. [ driver & enclosure obviously dependent ]
I should have stipulated that this 1cm 'felt blanket' should hang like a curtain being attached/glued only at its top.
Is it the extra extension in low bass you want or higher output level in low bass? What are the drivers in the current design and their sensitivities, especially woofer's comparing to the mid/treble section. Normally you want your woofer to be a few dB more efficient than the rest to compensate for baffle diffraction loses, min 3dB. Also placing the woofer/port close to boundary, say floor, can help make up for the lost output a bit. In case of two woofers in parallel the series inductor size will be reduced in half while the capacitor will have the twice the value. However the impedance will drop close to 2-3ohms in case of two parallel 8ohm woofers in 3way design at lower frequencies, which might prove problematic for some amplifiers. Why don't you add L-Pad network or similar attenuation network to midrange and tweeter to reduce their output comparing to the woofer and compensate for the baffle step loss in the woofer. I know it will require crossover redesign but it will lead to design done 'the right way'. BTW take a look at the Gema 3 way by SB, I know the crossover points are different and it's a huge old style box, but the driver placement with woofer close to the floor makes up for loss of bass due to baffle step.